ISSN:
1022-1352
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The preparation of multiblock copolymers poly[poly(L-lactide)-block-polydimethylsiloxane] by polycondensation of bifunctional oligomers via hydrosilylation is described. The procedure consists first to synthesize the two bifunctional oligomers α,ω-disilyl-polydimethylsiloxane and α,ω-diallyl-poly(L-lactide). The former is prepared in one step by cationic polymerization of octamethylcyclotetrasiloxane in the presence of 1,1,3,3-tetramethyldisiloxane as end-blocker. Two steps are necessary to prepare α,ω-diallyl-poly(L-lactide). The first one is the polymerization of L-lactide initiated by the system ethylene glycol/tin 2-ethylhexanoate. In a second step, the hydroxyl end-groups of the resulting α,ω-dihydroxy-poly(L-lactide) are transformed, by reaction with allyl isocyanate, into terminal allylic functions. Different multiblock copolymers were prepared by hydrosilylation (catalyzed by hexachloroplatinic acid) using the same α,ω-diallyl-poly(L-lactide) (M̄n = 2000 g · mol -1) and various α,ω-disilyl-polydimethylsiloxanes (M̄n from 1 750 to 9 000 g · mol -1). The influence of parameters such as temperature, stoichiometry of reactive end-groups and catalyst concentration on the molecular weight of the copolymers was studied. High molecular weight copolymers were obtained (DPn 〉 12 by SEC). In addition to the biodegradability of the lactic acid units, the immiscibility of the polydimethylsiloxane and poly(L-lactide) blocks imparts thermoplastic elastomer properties to these copolymers. The crystallinity of the poly(L-lactide) phase is dependent on the molecular weight of the polydimethylsiloxane blocks.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/macp.1995.021960130
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